Heat roller fixing type electrostatically charged image developing copiers and printers are gaining popularity because of widespread office automation. With this background, demand is growing for high grade or sharp copied or printed images which are highly light transmissive and well fixed. General formulations for toners in heat roller fixing type electrostatically charged image developing copiers and printers are shown in Table 1. One of the main factors for improving the sharpness, light transmission and strength of fixing of the image is a binder resin, a chief component of the toner. That is, a heat roller fixing type electrostatically charged image developing copier or printer feeds a toner to an electrostatically charged image on a latent image carrier to obtain a visible image, then transfers the resulting toner image to a plain paper or an OHP film, and fixes the transferred image. Currently, styrene-acrylate resin and polyester resin are widely used as binder resins. With the former resin, however, the light transmission and clarity of the resulting toner are not fully satisfactory, resulting in difficulty in obtaining a high grade image. The latter resin, on the other hand, imparts sufficient light transmission, but the resin is yellowish in color, thus decreasing clarity.
TABLE 1(Unit: wt. %)ChargeBinderColoringcontrolFunctioningMagneticresinagentagentagentpowderSolventDry two50–1000–200–100–20——componentsystemDry50–1000–200–100–20——nonmagneticonecomponentsystemDry magnetic 0–1000–200–100–200–60—onecomponentsystemLiquid toner15–50 0–100–5 0–10—50–70
The present invention has been accomplished in the light of the aforementioned problems. The object of this invention is to provide a toner in a dry two-component toner developer, a dry nonmagnetic one-component toner developer, a dry magnetic one-component toner developer, and a liquid toner developer which toner gives a higher grade copy image, namely, an image excellent in strength of fixing, light transmission and sharpness, in a heat roller fixing type electrostatically charged image developing copier or printer.